Abstract
The elongational flow behavior of polyethylene, polypropylene, polystyrene, poly(methyl methacrylate), and polycarbonate, temperatures from 70 to 290 °C and pressures up to 70 MPa, is examined with the Yahsi-Dinc-Tav (YDT) model and its particular case known as the Cross model. The viscosity data employed in the range of 3-405 s-1 elongational rates were acquired from the literature at ambient and elevated pressures. The predictions and the fitting results of the proposed YDT model with the same measurement data are compared with the Cross model. The average absolute deviations of the viscosities predicted by the YDT model range from 0.54% to 9.44% at ambient and 1.95% to 6.28% at high pressures. Additionally, the linear formulations derived from the YDT model are employed to relate the viscosity with temperature and hole fraction (“thermooccupancy” function) at zero level of elongational rate and constant elongational rate along with constant elongational stress. The effects of the four viscosity parameters (such as transmission and activation energy coefficients in these equations) on the elongational viscosity are analyzed in detail and some conclusions on the structural differences for the polymers are discussed.
Highlights
In rheology, flow is mostly a mixture of elongation and shear
The Yahsi-Dinc-Tav (YDT) non-Newtonian viscosity equation and the Cross-like model were employed to describe the correlation among the elongational viscosity and elongational rate as well as the rheological parameters of polymer
The results from the YDT model showed that the estimations were in good agreement with the experimental data both at ambient and at high pressures
Summary
Flow is mostly a mixture of elongation and shear. Elongational dominated, shear dominated, in rare cases pure shear, or purely elongational flow is the nature of this phenomenon. Zatloukal employed the proposed modified Leonov, the eXtended Pom-Pom and Advances in Polymer Technology the modification of White–Metzner equations for both shear and elongational flows of LDPE, mLLDPE, and PVB melts He tested a new modification of the Leonov model with a proposed dissipation term and showed that the model results are very good fitting for all flow situations. The dependence of elongational viscosity on hole fraction is analyzed in terms of linear equations derived from the YDT model at zero level of elongational rate, constant elongational rate, and constant elongational stress. From these derivations we obtained the viscosity parameters, e.g., transmission coefficient and a measure of activation energy coefficient, and related them with constant elongational rate and constant elongational stress
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
